– Holiday Cacti (2002)

By Leo A. Martin (December 2002)

Written by a “long-distance” member in Phoenix, this article was condensed from its original form. 

Schlumbergera (described by Lemaire in 1858) are sometimes called Thanksgiving or Christmas cactus, and rhipsalidopsis (described by Britton and Rose in 1923) are often called Easter cactus, because of when they bloom. Both require special attention here in Phoenix, but can be grown and flowered successfully. They are not so tolerant of forgetfulness as other cactus, so don’t expect great success if you’re absent-minded, like I am.

Schlumbergera now includes all species previously known as zygocactus and some previously known as epiphyllums. It contains around eight species and several varieties of each species. Rhipsalidopsis contains only three species and several varieties, some of which were previously included in epiphyllopsis, epiphyllum and hatiora.

Few people grow the species because the plants are easy to hybridize and grow commercially. The plants have red or purple flowers, but hybridizers have extended this range to whites, pinks, picotees, yellows and oranges.

Both schlumbergeras and rhipsalidopsis are South American jungle cacti, growing on tree branches well below the canopy and normally hanging downward in habitat. Both have stems segmented into flat pads. Aeroles are found on the edges of the segments at the bases of the small notches.

In cultivation, spines are almost microscopic or contained inside the body of the stems. Schlumbergeras often have small teeth on the edges of stem segments, but rhipsalidopsis lack these teeth. Their flowers are different, as well. Rhipsalidopsis flowers are radially symmetric, while schlumbergera flowers are zygomorphic, with a swan-neck shape to the tube and unequal petals.

Schlumbergeras are the easier to grow in Phoenix (and most other places). They come from wet forests of Brazil, where daytime temperatures are not as high as here, but cool night temperatures are common. In nature, their roots attach to tree bark and can be lightly covered with decaying leaf litter or bare and exposed. The roots are never dry for long because it rains a lot and humidity is high. The soft, succulent stems are flattened side to side to maximize surface area for photosynthesis.

This all adds up to a plant needing steady moisture, shade and protection from drying out. Roots will rot if the soil is too heavy or so wet that air is excluded. Roots die if the medium dries out for more than just a few hours. Schlumbergera cannot tolerate sun at all. They appreciate plentiful feeding and water.

Commercial growers raise schlumbergeras in humid greenhouses. Cuttings of two or three segments are placed in the shade until they shrivel slightly. Several cuttings are placed in a 3- to 4-inch pot using almost pure peat moss. They are kept on the dry side until rooted, then watered regularly, with dilute fertilizer applied. Unfortunately, I haven’t found a good way to root cuttings. Most of mine rot.

The trick in growing these plants is keeping the roots healthy, with a moist environment and some air circulation. Soil must drain rapidly, retain some moisture and be easily rewetted. The peat used by growers is not a good idea for hobbyists — it dries too quickly. Heavy soils, however, exclude oxygen, which is death for epiphytic roots. I am still experimenting to find a soil mix I like.

Schlumbergeras grow vigorously all spring and summer, producing several new stem segments and new branches. They slow down as fall progresses. Bud formation is triggered by lengthening nights or night temperatures that routinely drop below 55 degrees.

Commercial growers manipulate night length by draping heavy fabric over the plants to produce blooming plants at any time of the year. Forgetting to place the fabric even once resets the plants’ clocks. Similarly, inside a house, a few minutes of artificial light at the wrong time will prevent buds from forming. Also, few people allow their home’s temperature to drop below 55 degrees, so their plants never bloom.

When buds form, they are fragile, and plants often drop them if moved while in bud. It is best to allow the buds to open, then place the plant for display. If put outside at night, blooming plants will hold their flowers longer – but avoid frost.

Most people buy schlumbergeras in bloom in November or December. After making so many flowers, the stems shrivel a little. At this point, the plants need a dryish rest with stretched-out watering periods. After four to six weeks of winter rest, the plants will suddenly sprout new growth.

For new plants, now is the time to repot. Rinse off the peat-based soil and replant in a slightly larger pot using a mix with some organic matter but lots of air space. Some people use orchid bark mixed with pumice or perlite. Some use bagged potting soil, which never worked for me. Water immediately and put in a cool spot, and the plant should continue growing. Remember the light and temperature issues, and your plant is sure to bloom again.

Rhipsalidopsis are harder to grow than schlumbergeras. To start with, the plants are very fragile. Stem segments drop off with a slight bump. Although they do root more easily for me than schlumbergeras, the plants require higher humidity and die quickly without it. My best results came from growing rhipsalidopsis in the bathroom, where I had to look at them every day, or in the winter in my sunroom, which is quite humid.

To compensate for their greater requirements, they are not light-sensitive. If you can keep them alive until spring, you will be treated to a great show of flowers.